Self-toning photographic emulsion



Patented May 8, 1923.

UMEE states titans rarest cri ics;

EDMUND n. BULLOCK, or nocrins'rna, new Yoa'x, rissienon '10 nas'rlueu KODAK GQMPANY, or noonnsrnn, NEW YORK, a oonroaarrou on NEW roan.

sELn'rom'ue rrio roc-nnrmo nra ntsrolv.

No Drawing.

T 0 all whom it may concern Be it known that I, EDMUND R. BULLOCK, a subject of the King of Great Britain, residing at Rochester, in the county of Monroe and State'of New York, have invented certain new and useful Improvements in Self-Toning Photographic Emulsion, of which thefollowing is a full, clear, and exact specification.

This invention relates to photographic emulsions and particularly to those of the type known as printing-out, that is, upon which light makes a strongly visible i1npression; and still more particularly to the type known as self-toning, that is, in which the image assumes a desirable colored tone in regular photographic treatment without special toning baths.

It has been customary to make self-toning, printing-out emulsions containing gold compounds. I have discovered that if, instead of gold, a tellurium compound, and particularly a complex .tellurium salt, is used, an emulsion having desirable properties may be made.

Following is an example of an emulsion embodying my invention. The figures in each case represent parts by weight.

A: Ammonium chloride, 12; soft gelatin, 22: water, 1700.

B: Silver nitrate, 36; water, 40.

C: Trisodium citrate, 8; hard gelatin, 22; water, 340.

D: Silver nitrate, 10; citric acid, 18; water, 40.

E: Tellurium dioxide, 1; sodium hydrogen tartrate, 12; water, 250.

. Each of the above mixtures is made separately. Mixture A is then heated until the gelatin is dissolved in the water, whereupon solutions A and B are emulsified together, silver chloride being formed, and the resulting emulsion is allowed to set, squeezed. through canvas and washed. Mixture C is r then heated until the gelatin is dissolved,

and solutions C and D are then emulsified together at as low a temperature as possible Application .filed January 13, 1922. I Serial No. 529,079.

without setting the gelatin. Silver citrate is formed in the emulsion thus formed, which is allowed to set and then slightly washed.

To dissolve the tellurium dioxide in E, s0Ine-,

the dilution state d. Finally the emulsions A-I-B, and C-l-D are re-meltedand mixed with each other and with solution E and coated on a suitable support, usually paper, in the customary way. It may be noted that the emulsion made by A+B and C+D to-' gether is a known printing-out emulsion, containing the sensitlve silver salts mentlOIlQCl and some fIeQCltIlC acld. Many other known formulae for printing-out emulsions mi ghtbe used and mixed with solution 33. As free acid is undersirable in" some emulsions of this type, the solution E can be neutralized with sodium carbonate when these are used.

The coated emulsion keeps well. It may be printed upon in the manner usual with printing-out papers. Printing is continued until a depth of image such as is usually required with printing-out emulsions is at-. rained. Combinedtoning and fixing of the image is effected by direct immersion in a limited volume of hypo solution, (forexample, one ounce of 15% solution of crystallized sodium thiosuliate to every 15 square inches of emulsion area) followed by a fresh bath of hypo solution ofunlimited volume and washing. The second hypobath is not s rictly'essential but is found to be desirable. for permanency of the print.

It is to be understood that the above is but an example and that I contemplate as included in my invention all such equivalents as fall within the scope of the ap pended claims.

Having thus described my invention What I claim as new and desire to secure by Letters Patent is:

1. An emulsion containing a sensitive sil- Yer salt and a tellurium compound.

2. An emulsion containing a sensitive sil- Yer salt and a complex tellurium salt.

3. An emulsion containing a silver halide and a tellurium compound.

4. A self-toning, printing-outemulsion containing a silver halide and a complex tellurium salt.

5. A self-toning, printing-out emulsion containing silver chloride and a complex tellurium salt.

6. A self-toning printing-out emulsion containing silver chloride and sodium-telluryl-tartrate.

Signed at Rochester, New York, this 7th day of January 1922.

EDMUND R. BULLOCK. 

